New toy... Infrared thermometer

[andrewh]

Having starts the newly rebuilt engine and being a tad wary of it getting hot ( had a problem on a Rover V8 recently after rebuild due to air locks) I have treated myself to an infrared temperature gauge. Now question is the dash temp had me between 70 to 80 degrees but the fan did not kick in ( its a 62 3.8 with fan relay). I have checked the wiring and the motor and all well, brand new relay but not checked that yet. Thing is the engine seemed hotter to me hence the new toy. Anyone want to guide me on some acceptable temperatures to look for on the engine? What for instance should the thermostat open at and what would be acceptable temperatures for cylinder head and block without the fan kicking in. Whether the fan does any good anyway we wait to see.

Lastly , are the engine cooling systems prone to air locks? It's throwing out the top inch or so of water from the expansion tank so you see the baffle above the water. Seems odd, no loss anywhere I can see just seems to be hot, but reading only 75 ish as stated

[Dave K]

Andrew,

A few years ago I had a conversation with Rob Beere about engine cooling and about the water wetter coolant additives. He was telling me that using water wetter or similar is a good idea because it stops the water boiling close to the exhaust manifold area of the block / head and therefore really helps in the keeping the engine cooler. I also have a vent fitted at the highest part of the cooling system to make sure all the air is out of the system. There was a lot more to it but thats about all I can remember, don't know if it helps you at all?

Dave

[Heuer]

If you are going to use the laser infra red gun to get accurate readings you need to put a piece of masking tape on any shiny metal surfaces and take the reading off that. As Dave points out air locks can be a problem on the 3.8 so try removing the temperature sender and see if there is coolant in the manifold rail.

Jaguar supplied two types of thermostat which opened at different temperatures - stamped 74C or 88C meaning they will open when the water temperature reaches that figure. The 88C one is for use in "cold climates", and despite what we all feel at the moment, the UK does not count! There are a few types of thermostat knocking about - the plain type with no air valve and the original type which has the air valve. Both should work fine but if you are troubled ask SNG for the original rather than pattern type - only cost about ?3 anyway. The toggle helps with air locks but should not be necessary.

[abowie]

I have checked the wiring and the motor and all well, brand new relay but not checked that yet.

Short the otter switch wires; the fan should come on.

[andrewh]

Well, thank you for the various tips and suggestions . The thermostat is definitely ok as you can notice it open when the rad starts to get warm . Will be interesting to see at what temp that happens. Reference he shorting of the two otter switch wires, I think I may have done that , or just earthed the feed and the fan did not come on. Hence I went back through the system so I will recheck but that of course points to a faulty fan relay. Ummh.

Reference the air in the system I may run it for a while with the cap off which should help purge some air if there is some in there. It can hardly fail to trap air when you think of those bulk heater heater pipes etc.

Lets hope the new infrared thermo arrives soon.

[andrewh]

I have checked the wiring and the motor and all well, brand new relay but not checked that yet.

Short the otter switch wires; the fan should come on.

Of course you were quite correct. I had shorted these and then went back through all the electrics withou arriving at the view the relay was U/S

I connected the old 50 year old relay which was fine. Thanks